Project Summary/Abstract The Principal Investigator?s (PI) goal is to be a scientist in an academic setting with a research program focused on understanding adolescent substance use and identifying key targets for prevention efforts. A comprehensive training plan was therefore constructed to systematically advance the PI?s training in: 1) developmentally-relevant risk factors, comorbidity, assessment tools, and sophisticated research related to social anxiety (SA) among youth; 2) developmentally-relevant risk factors, comorbidity, assessment tools, and sophisticated research related to marijuana use among youth; and 3) the development, implementation, analysis, and dissemination of prevention programs that target youth. Importantly, the proposed study is designed to complement the training program by helping the PI to refine relevant research skills while completing an initial test of factors related to adolescent marijuana use. The proposed sample will include 120 youth (15-17 years) endorsing recent marijuana use. Among adults, SA is positively related to marijuana problems; however, no work has examined this among youth. To address this gap, the proposed study was designed to replicate findings with an adolescent sample in a controlled lab setting. Youth will be randomly assigned to either a peer rejection or neutral cue and then assessed on their degree of willingness to accept a series of simulated marijuana offers. Marijuana use problems, SA, and relevant risk factors will be assessed with continuous self-report measures and structured interviews at baseline. Together, SA and rejection are expected to positively relate to real-time marijuana use willingness and use problems. Marijuana use motives and history also will be examined as potential explanatory mechanisms by which SA and negative responding to rejection may lend to the development of problems. The proposed project aligns with the strategic plan outlined by the National Institute on Drug Abuse in 3 key ways. First, the aims of the research project are to gain a better understanding of risk for developing marijuana use problems before they occur through the dual examination of individual (e.g., SA) and contextual (e.g., peer rejection) factors in a controlled laboratory setting. Second, the novel application of this work to an adolescent sample ensures that the data from this project will be meaningful for prevention efforts- even if the specified hypotheses are not supported. Indeed, the findings stand to either replicate observations seen with adults or highlight features that differentiate younger, less-experienced users. As such, this study will lay the foundation for future work in this area that can lend to more targeted, and thus more effective, prevention programs. Finally, the project will serve as an important training opportunity for the PI through tailored training in the development of her independent research program targeting prevention-oriented substance use work among adolescents.